Comments on: Second H1N1 peak in US

By: H1n1 Recall

H1n1 Recall — Wed, 09 Dec 2009 08:00:00 +0000

[...] Second H1N1 peak in US (virology.ws) – November 20, 2009Recall the the first wave of H1N1 infections that took place during the spring and summer: influenza-week-23. It’s interesting to note that seasonal H1N1 and H3N2 strains are nearly gone. Of the 10803… [...]

By: wii spiele

wii spiele — Thu, 26 Nov 2009 06:05:06 +0000

Hi,
Could you point me to a reference for this? I've never heard it before, and given that we've only had 4-5 pandemics in the past century it seems surprising that you can be so confident. It's not at all consistent with the 1918 influenza in the US, and I'm not aware of anything showing such waves for the 1957, 1968, or 1977 pandemics. I know of the 2006 Science paper showing waves in normal seasonal flu (6-7 week waves for H1N1, 3-4 weeks for H3N2) but that's quite a different thing, not reflecting national incidence.

By: profvrr

profvrr — Wed, 25 Nov 2009 16:30:16 +0000

That's never been shown to be a consequence of original antigenic sin.
If immunization is against antigenically distinct strains one would
simply expect that the new strain would not be recognized by the
memory response. No reason to believe infection with the novel strain
would be worse.

By: Bo Liang

Bo Liang — Mon, 23 Nov 2009 15:15:41 +0000

If this is the case, would it mean that the vaccination against other strains could render people more susceptible to newly emerging “novel” strain?

By: profvrr

profvrr — Mon, 23 Nov 2009 14:39:33 +0000

That is a great question which no one has ever been able to answer.
It's been seen before. For example, in 1957, when the H2N2 pandemic
strain emerged, the H1N1 strains that had been circulating since 1918
disappeared. In 1968, when the pandemic H3N2 strain emerged, the H2N2
strains went away. One idea is 'antigenic sin', which says that when
the new strain emerges, it stimulates a strong memory response to
influenza viruses that have previously infected the host. But it's not
clear if that explains everything.

By: Bo Liang

Bo Liang — Mon, 23 Nov 2009 14:36:00 +0000

I was wondering what is the reason for seasonal H1N1 and H3N2 infection diminishes so dramatically as the pandemic H1N1 prevailing? Is it because the pandemic H1N1 are more infective than the others? If the pandemic H1N1 and other strains infect a person simultaneously, would the pandemic H1N1 out-grow the other strains?

By: profvrr

profvrr — Mon, 23 Nov 2009 12:41:27 +0000

It is possible that some 2009 H1N1 virus was circulating early in
2009; in fact sequence analysis suggests that the virus originated
towards the end of 2008. However I believe it's likely the strain
would have been detected. Even though many strains are not subtyped,
enough of the swine-origin virus would have cropped up as 'untypable'
to warrant further analysis. Which is what happened in California and
Texas in April 2009.

By: Eileen

Eileen — Sat, 21 Nov 2009 18:43:23 +0000

Couldn't there have been a lot more swine flu around in the beginning of the year from, say, week 1 through 12? I'm looking at all those “A (Subtyping not Performed)”, for instance, and wondering how many (if any) were swine flu.

By: pjenks

pjenks — Fri, 20 Nov 2009 22:39:37 +0000

Some mathematical biologists at Purdue made a pretty impressive prediction of a 42nd week peak, back in September:

http://www.eurosurveillance.org/ViewArticle.asp...

They did a fit using a seasonally-driven SIR model and the CDC data from weeks 22-33. They don't show what that fit does in the coming spring…

I agree there will be another peak of flu in the Spring, but I imagine it will be seasonal.